1. Field of the Invention
The present invention relates to a Bluetooth private network and communication method thereof, and particularly to a Bluetooth private network with a handoff function to enable a Bluetooth device to be used with multiple Bluetooth access points without interruption.
2. Discussion of the Related Art
First, hereinafter description will be made about Bluetooth. In order to solve the problem that too many connecting cables are required for the connection among movable devices, Bluetooth was developed on February 1998 under the cooperation of movable telecommunication providers and computer manufacturers including Ericsson, Nokia, Intel, IBM and Toshiba. Bluetooth is a new radio telecommunication technology based upon low cost, low electric power radio communication and aims for replacing cables, and realized into a chip-type solution since it can be installed in various kinds of portable devices.
Bluetooth allows direct radio communication among devices without passing through a remote base station when inter-device data transmission is required at home or office so that data can be freely transmitted at high speeds without any standby time, while causing no communication load to the base station. Also, the inconvenience that an average consumer should connect and maintain communication cables one by one in the house is solved, and integration is promoted among information devices, such as a computer, and communication devices, such as a telephone.
Bluetooth has the following features. Frequency is 2.4 GHz ISM (Industrial, Scientific and Medical) band for allowing realization with relative ease and low price, and the distance of transmission is 10 meters. The transmission distance is determined 10 meters based upon the judgement that 10 meters is sufficient for the transmission between a portable device of a user and a device installed on a desk in the office. Time division is adopted as a multiplexing to lower price, and three synchronous channels and one asynchronous channel are provided. For communication, Gaussian filtered FSK (GFSK) is used as a modulation mode, circuit and packet switch is employed, and a pico cell is formed.
FIG. 1 shows a connecting method via a Bluetooth system. As shown in FIG. 1, the connecting method includes a point-to-point connection and a point-to-multipoint connection. A master should be discriminated from a slave in Bluetooth, in which the master orders a command and the slave receives and performs the command. According to Bluetooth, the slave can communicate only with its master, and should pass by the master for the communication with other slaves. Bluetooth allows seven active channels, in which the master can be connected with up to seven active slaves.
However, even in Bluetooth, the connection is interrupted during movement from one piconet to another piconet, incurring packet loss. Support for mobility and handoff is required to solve this problem, whereas, at the present, Bluetooth does not provide such mobility.